1. Field of the Invention
The present invention relates to a transmission in which a driving force of a driving source is transmitted to a transmission gear via a sun gear and a planetary gear and, in particular, to a transmission including a switch that detects a rotation position of a rotary member for revolving the planetary gear. Further, the present invention relates to a communication apparatus including the transmission.
2. Discussion of Related Art
For example, in a communication apparatus such as a facsimile apparatus, there is adopted a configuration in which a driving force of one motor is transmitted to selected one of a plurality of driving portions. These driving portions correspond to various actions, e.g., feeding of a document or a recording sheet, reading of an image of the document, or recording the image onto the recording sheet. There is adopted a transmission as a mechanism for selectively transmitting the driving force. There has conventionally been a transmission in which a driving force of a motor is transmitted to a transmission gear via a sun gear and a planetary gear, as disclosed by Patent Document 1 (JP-A-2002-257210) or Patent Document 2 (JP-A-2006-7606).
In FIGS. 22, 23 and 24, there is shown a manner of switching or changing driving-force transmitting modes in a conventional transmission. Two-planetary gears 201, 202 are rotatably supported by a cam plate 200 as a rotary member. The cam plate 200 has a generally circular-disk shape and is rotated about its center as a rotation axis. Each of the planetary gears 201, 202 supported by the cam plate 200 is revolved with a rotation of the cam plate 200. Although not shown in FIGS. 22 through 24, a sun gear is provided so as to be coaxial with the cam plate 200. When a driving force is transmitted from the sun gear to the cam plate 200 via a clutch, the cam plate 200 is rotated counterclockwise (hereinafter, called as “a forward rotation” or described a “forwardly rotated”) or rotated clockwise (hereinafter, called as “a reverse rotation” or described as “reversely rotated”). Further, the sun gear and each of the planetary gears 201, 202 are meshed with each other. Therefore, the respective planetary gears 201, 202 can be revolved around the sun gear, and can also be rotated by the driving force transmitted from the sun gear.
At five predetermined positions around the cam plate 200, there are respectively provided five transmission gears 203, 204, 205, 206, 207. Depending on a rotation position of the cam plate 200, one of the transmission gears 203-207 is meshed with one of the planetary gears 201, 202. For instance, at a rotation position of the cam plate 200 shown in FIG. 22, the planetary gear 201 is meshed with the transmission gear 203 for thereby transmitting the driving force therebetween; and at a rotation position of the cam plate 200 shown in FIG. 23, the planetary gear 202 is meshed with the transmission gear 205 for thereby transmitting the driving force therebetween. The cam plate 200 is provided with a stopper 208. When the stopper 208 is engaged with a hole of a frame, not shown, whereby the cam plate 200 is stopped at a predetermined rotation position.
In a peripheral portion of the cam plate 200, there are provided a plurality of projecting portions 209, 210. The cam plate 200 includes six projecting portions. However, in each drawing, reference numerals are used to designate only two of the six projecting portions that are actually shown. A switch 212 is disposed adjacent to the cam plate 200. A switch lever 213 of the switch 212 is swung or pivoted by each of the projecting portions 209, 210. Owing to a swing of the switch lever 213, the switch 212 is turned ON, i.e., the switch 212 is in an ON state. A rotation position of the cam plate 200 is judged on the basis of the ON/OFF state of the switch 212 and a number of pulses generated in a pulse motor (not shown) functioning as a driving source.
As shown in FIGS. 22 and 23, when the cam plate 200 is rotated counterclockwise (i.e., forwardly rotated) in the conventional transmission, the changing of the driving-force transmitting modes, namely, the changing of combinations of one of the planetary gears 201, 202 and one of the transmission gears 203 through 207 between which the driving force is transmitted, is conducted. Further, as shown in FIGS. 22 and 23, when the cam plate 200 is rotated clockwise (i.e., reversely rotated) in the conventional transmission, the driving force is transmitted between an appropriate one of the planetary gears 201, 202 and an appropriate one of the transmission gears 203 through 207. For instance, when the cam plate 200 is rotated from the rotation position shown in FIG. 22 to the rotation position shown in FIG. 23, the driving-force transmitting mode in which the planetary gear 201 and the transmission gear 203 are meshed with each other is switched or changed to the driving-force transmitting mode in which the planetary gear 202 and the transmission gear 205 are then meshed with each other.
A rotation direction of the cam plate 200 is changed from the forward rotation to the reverse rotation, or vice versa, when a rotation direction of the pulse motor is changed likewise. A timing for changing the rotation direction of the cam plate 200 is controlled on the basis of the ON/OFF state of the switch 212 and the number of pulses of the pulse motor as the driving source.